On Sunday, the office of her husband, former President George Bush, issued a statement saying that after consulting her family and her doctors, Mrs. Bush had “decided not to seek additional medical treatment and will instead focus on comfort care.”

The Bushes had celebrated their 73rd wedding anniversary in January, making them the longest-married couple in presidential history.

Mrs. Bush had been hospitalized with pneumonia in December 2013. She underwent surgery for a perforated ulcer in 2008 and had heart surgery four months later.

As the wife of the 41st president and the mother of the 43rd, George W. Bush, Mrs. Bush was only the second woman in American history to have a son of hers follow his father to the White House. (Abigail Adams, wife of John Adams and mother of John Quincy Adams, was the first.)

During that campaign, he was repeatedly derided in personal terms by the eventual nominee and now president, Donald J. Trump, prompting Mrs. Bush, who was never shy about expressing her views, to lash back, suggesting in television interviews that Mr. Trump was a misogynist and a hatemonger.

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Barbara Bush with her husband and a very young George W. Bush in 1955 in Rye, N.Y., where Mrs. Bush grew up.CreditGeorge Bush Presidential Library, via Associated Press

“He’s said terrible things about women, terrible things about the military,” Mrs. Bush told CNN. “I don’t understand why people are for him.”

Dedicated to her family and largely indifferent to glamour, Mrs. Bush played down her role in her husband’s political success. But she was a shrewd and valuable ally, becoming a sought-after speaker in at least four national campaigns: in 1980, when Mr. Bush was chosen to be Ronald Reagan’s running mate; in 1984, when the two ran for re-election; in 1988, when Mr. Bush campaigned for president; and in 1992, when he sought re-election.

She stepped into another presidential campaign in 2000, that of her son George, then the governor of Texas. She appeared at fund-raisers and met voters in New Hampshire and other states on his behalf as he rolled to the Republican presidential nomination.

She was clearly a political asset. A 1999 poll found that 63 percent of Americans had a favorable opinion of her and that only 3 percent had an unfavorable one.

Outspoken and Combative

While first lady, from January 1989 to January 1993, Mrs. Bush generally refused to talk publicly about contentious issues, particularly when her opinion was said to differ from her husband’s.

“I’m not against it or for it,” she said of the Equal Rights Amendment in 1989. “I’m not talking about it. I want equal rights for women, men, everybody.”

There were rumors that she favored abortion rights, but she made it clear that she supported her husband and would not say whether she was comfortable with his anti-abortion stand.

She was vocal, however, in championing causes of her choosing. Literacy was one, and so was civil rights; she had been an early supporter of the movement.

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Mrs. Bush reading to children at a day care center in New York in 1990. Literacy and civil rights were two causes she championed.CreditWilliam E. Sauro/The New York Times

And she could be combative in news interviews, sometimes yanking off her glasses and tartly chastising reporters when she thought they were being overly aggressive.

Her candor occasionally got her into trouble. In 2005, while visiting victims of Hurricane Katrina at the Houston Astrodome, where they were being temporarily housed, she remarked that many of them “were underprivileged anyway” and that their Astrodome stay — though the living conditions there were dire — was “working very well for them.”

The comments, coming at a time when her son’s administration was being roundly criticized over its response to the storm, were widely heard as insensitive and condescending.

Two years earlier, shortly before President George W. Bush ordered the invasion of Iraq, she said in a television interview that she had not been watching coverage of the prelude to war. “Why should we hear about body bags and deaths, and how many, what day it’s going to happen?” she asked. “Why would I waste my beautiful mind on something like that?”

She was similarly outspoken in 2013 when she was asked, on the “Today” show, if she thought her son Jeb should run for president in 2016. “I really don’t,” she replied, adding, “There are other people out there that are very qualified, and we’ve had enough Bushes.”

She later changed her mind. In an email to potential supporters in March 2015, she acknowledged, “When the idea of Jeb running for president first came up, I was hesitant.” But she said she was starting a “Run Jeb Run Fund” because “Jeb is our best chance of taking back the White House in 2016.”

She went on to campaign for him in New Hampshire, but he finished fourth in the Republican primary there in February and suspended his campaign a few days later.

Mrs. Bush enjoyed a favorable public image throughout her years as first lady. In one respect she benefited from comparisons with her predecessor, Nancy Reagan, whom many perceived, rightly or wrongly, as remote, icy and overly style-conscious.

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Mrs. Bush with her son Jeb at a rally in Derry, New Hampshire in 2016.CreditStephen Crowley/The New York Times

By contrast, Mrs. Bush was regarded as unpretentious, a woman who could wear fake pearls, enjoy takeout tacos, walk the dog in her bathrobe and make fun of herself. Perhaps adding to her appeal, she conformed to the popular view of an old-fashioned grandmother, with her white hair and matronly figure; though she was almost a year younger than her husband, many thought she looked much older.

“What not everyone always understood is that Barbara revealed as much as she wanted to but seldom more,” Donnie Radcliffe wrote in a 1989 biography, “Simply Barbara Bush: A Portrait of America’s Candid First Lady.” “She came into the White House with a dexterity at manipulating her image, and she wasn’t above playing off her own outspoken style against Nancy Reagan’s reluctance and often inability to express herself.”

“A less popular political wife,” Ms. Radcliffe added, “might have seemed calculating.”

Part of Mrs. Bush’s popularity stemmed from her penchant for self-deprecation. Soon after moving into the White House, she said, “My mail tells me a lot of fat, white-haired, wrinkled ladies are tickled pink.”

She would do anything asked of her to help the Bush administration, she said, but she drew a line: “I won’t dye my hair, change my wardrobe or lose weight.” Even so, as first lady she was known to wear designer clothes and have her hair styled.

For all her joking about herself, she also confessed that she had felt like crying after Jane Pauley told her on the “Today” show, “Mrs. Bush, people say George is a man of the ’80s and you’re a woman of the ’40s.”

An Invisible Influence

Mrs. Bush often insisted that she stayed out of her husband’s concerns. But few who knew her believed that she would ever hesitate to tell Mr. Bush her views.

“You have to have influence,” she said in 1992. “When you’ve been married 47 years, if you don’t have any influence, then I really think you’re in deep trouble.”

The substance of that influence remained largely invisible to the public eye, however, making her one of the few first ladies of her era to escape serious criticism. When Mrs. Reagan raised more than $1 million in tax-deductible contributions in 1981 to redecorate the White House living quarters, there was a public outcry. When the Bushes’ friends raised almost $200,000 to spruce up the vice-presidential house the same year, there was hardly a stir.

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Mrs. Bush in a 1988 portrait of the Bush clan outside St. Ann's Church in Kennebunkport, Me., during her husband’s vice presidency. George W. Bush sits next to Mrs. Bush.CreditPaul Hosefros/The New York Times

“I got away with murder,” Mrs. Bush said shortly before her husband’s inauguration.

One glaring exception came in 1984. Speaking of Representative Geraldine A. Ferraro of New York, the Democratic nominee for vice president, Mrs. Bush characterized her as something that “rhymes with rich.” She later apologized, but even then she parried with her critics, saying she did not mean any offense by calling Ms. Ferraro “a witch.”

She was born Barbara Pierce on June 8, 1925, at a maternity hospital in New York City run by the Salvation Army principally for unwed mothers. The family obstetrician practiced there one month a year, and that month happened to be June. She was the third child of the former Pauline Robinson and Marvin Pierce. Her father was in the publishing business and eventually became president of the McCall publishing company. Her mother, the daughter of an Ohio Supreme Court justice, was active in civic affairs in Rye, N.Y., the New York City suburb where the family lived.

One of Mrs. Bush’s distant relatives was Franklin Pierce, the 14th president of the United States.

Barbara was brought up in considerable affluence. She attended the public Milton School and the private Rye Country Day School and, along with her contemporaries, suffered through dancing classes, which she never forgot. “I was 5 feet 8 inches at the age of 12, and it certainly bothered the boys,” she recalled.

Her final two years of high school were spent at Ashley Hall, a boarding school in Charleston, S.C. A classmate once described it as a place where “being bad meant taking off your hat and gloves when you got out of sight of the school.”

Long Romance Begins

She met George Bush in 1941 at a Christmas dance at the Round Hill Country Club in Greenwich, Conn. George had grown up in Greenwich, a son of Prescott S. Bush, a Wall Street executive and a future United States senator from Connecticut, and the former Dorothy Walker. At the time, he was a senior at Phillips Academy in Andover, Mass. They began corresponding.

After graduating in 1942, Mr. Bush enlisted in the Navy and trained as a pilot. The next year, he was assigned to a torpedo squadron in the Pacific and piloted a Grumman Avenger. On one combat mission, in 1944, he was shot down and rescued by a submarine. Barbara did not hear from him for a month.

After enrolling at Smith College but before entering the freshman class, she shocked her mother by spending the summer working in a nuts-and-bolts factory.

She and Mr. Bush, on leave from the Navy, married in Rye on Jan. 6, 1945; the bride, not yet 20, had dropped out of Smith at the beginning of her sophomore year. “The truth is, I just wasn’t interested,” she said in interviews. “I was just interested in George.”

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Mrs. Bush at a 2015 presidential campaign rally in Miami for her son Jeb. “When the idea of Jeb running for president first came up, I was hesitant,” she once said, but she changed her mind. Mrs. Bush is flanked by Columba Bush, Jeb’s wife, and George P. Bush, his son.CreditStephen Crowley/The New York Times

They honeymooned in Sea Island, Ga., and spent nine months at military bases in Michigan, Maine and Virginia before Mr. Bush was discharged and entered Yale. In New Haven, where the couple moved, their first son, George, was born in 1946.

After Mr. Bush’s graduation, in 1948, the family left for Texas, where Mr. Bush, with the help of a family friend, had taken a job as an equipment clerk in the oil industry. For a time, in Odessa, Tex., the family lived in one half of a house; the other half was used as a brothel. Within a year they were sent to California. A daughter, Pauline (known as Robin), was born there in 1949 but died of leukemia before her fourth birthday.

The California sojourn was brief; the Bushes soon returned to Texas — first to Midland, where they bought a house in a neighborhood known as Easter Egg Row because the houses were all painted in pastel colors, and later to Houston. By the time the Bushes reached the White House, they had moved 26 times.

In Texas, four more children were born: Jeb (John Ellis) in 1953, Neil Mallon in 1955, Marvin Pierce in 1956 and Dorothy Walker in 1959. Only George and Jeb went into politics; Neil and Marvin became businessmen, and Dorothy Bush Koch became a philanthropist.

Mrs. Bush’s children survive her, as do her husband; her brother, Scott Pierce; 17 grandchildren; and seven great-grandchildren.

Every summer, while Mr. Bush was engaged in oil deals and raising investment money, Mrs. Bush and the children drove to the Bush family compound in Kennebunkport, Me.

On her first trip there, Mrs. Bush discovered that the hotel where she had made reservations along the way would not accommodate two black family employees who were accompanying her and the children. The employees said they would find another place. But Mrs. Bush refused to split up the group and found other accommodations. On becoming first lady, she insisted that her press secretary be black — a first for that position.

The family moved to Washington in 1966, when Mr. Bush, after an unsuccessful run for the Senate in 1964, was elected to the House of Representatives from Texas’ Seventh Congressional District, which includes parts of Houston. He served two terms and mounted a failed second campaign for the Senate.

Later, as compensation for giving up his safe seat in the House to make the Senate run, he was named ambassador to the United Nations by President Richard M. Nixon. He assumed the post in 1971, and the Bushes moved into the ambassadorial suite of the Waldorf Towers in New York.

Lifelong Volunteer

The family returned to Washington in 1973 when Mr. Bush was appointed chairman of the Republican National Committee, a position he occupied during the Watergate crisis. In 1974, President Gerald R. Ford sent him to the People’s Republic of China to lead the United States Liaison Office in Beijing.

“Watergate was a terrible experience,” Mrs. Bush told Ms. Radcliffe in 1984. “So to go off to China and learn a whole new culture was beautiful.”

She particularly liked having her husband to herself; their children had not accompanied them. The two cycled around Beijing, studied Chinese and learned tai chi.

In “Barbara Bush: A Memoir,” published in 1994, Mrs. Bush acknowledged that she suffered from depression in 1976 after she and her husband had returned from his two-year China posting and he was named director of the Central Intelligence Agency, a post he held for 11 months.

She had discussed her depression at a news conference in 1989, saying she believed that the women’s movement had contributed to her illness. “I believe it made me feel inadequate,” she said. “I’m not quite sure how. You were made to feel demeaned a little bit.”

Mrs. Bush published another memoir, “Reflections: Life After the White House,” in 2004.

A lifelong volunteer for charitable causes, Mrs. Bush raised money for the United Negro College Fund while in New Haven, started a thrift shop in Midland and volunteered in nursing homes and hospitals in Houston, Washington and New York. Her son Neil’s dyslexia led to her interest in fighting illiteracy.

In her eight years as the wife of the vice president, she attended more than 500 events related to literacy, and after she became first lady she started the Barbara Bush Foundation for Family Literacy. The profits from her book “C. Fred’s Story: A Dog’s Life” (1984), a wry look at Washington life as seen by her dog, and from a follow-up based on another family dog, “Millie’s Book: As Dictated to Barbara Bush” (1990), went to literacy causes.

Mrs. Bush hoped her contributions to those causes would form a large part of her legacy.

“I want to be known as a wife, a mother, a grandmother,” she wrote in 1988. “That’s what I am. And I’d like to be known as someone who really cared about people and worked very, very hard to make America more literate.”

Correction:April 19, 2018

An earlier version of a picture caption with this obituary misstated where in Kennebunkport, Me., the 1988 photo of the Bush family was taken. It was in front of St. Ann’s Church, not at the Bush family compound.

A version of this article appears in print on , on Page A1 of the New York edition with the headline: Barbara Bush, First Lady and First Mother, Dies at 92. Order Reprints | Today’s Paper | Subscribe